Apparatus for lamp manufacture



March 31, 1942 I E. c. cURwEN ETAL 2,277,691

APPARATUS [For: LAMP MANUFACTURE Filed Aug. 6,"1940 Pzc- HEAT/N 6 Fw@ Mcm/M ERNEST C; CURWEN ROLAND M.GARDNE.R

1N VENTOR.

ATTORNEY exhaust cycle.

Patented Mar. 3l, 1942 PATENT yOFFICE 2.277.691 APPARATUS Fort LAMP MANUFACTURE Ernest C. Curwex Salem, and Roland M.V Gardner, Swampscott, Mass., assigner-s to Hygrade Sylvania Corporation, Salem, Mass., a corporation of Massachusetts` Application August 6', 1940,'Serial No. 351,596

2 Claims.

This invention refers to an exhaust-machine for electric gaseous discharge lamps and more particularly to an exhaust schedule for such a machine.

An object of this invention is to provide an exhaust cycle that will properly and adequately exhaust fluorescent lamps.

Another object is to provide an exhaust cycle to which a heating overffor aiding the exhaust may be readily adapted.

A further object is to provide an exhaust cycle inwhich several separate exhaust lines are used,

thereby obtaining a higher purity atmosphere in the lamp when it is being exhausted.

Another object is to obtain'an exhaust cycle which will provide for an adequate cathode break-down.

Another object is to provide an exhaust cycle to which a means for testing the lamps before they are tipped oil' may be readily adapted.

Another object is to provide an exhaust cycle to which a mercury dispensing means may be readily adapted.

Another object is to provide an exhaust cycle to which a means for controlling the pressure of the gas filling may be readily adapted.

Another object is to provide an exhaust cycle to which a means for tipping o the lamps may be readily adapted.

Further objects and advantages of this invention will be .apparent from the speciiications which follow taken in conjunction with the accompanying drawing.

The accompanying schematic diagram shows the desired arrangement of the steps and processes through which the lamp goes during the complished through a circular series of thirtytwo heads. The function of each individual head is determined in accordance with its position in relation to the preferred order of the steps and processes which the lamp should undergo.

Positions 2, 3, 4, and 5 vare loading and discharging positions, i. e., they may be used for either purpose.y Lamps to be exhausted may be loaded on to the machine at positions 3 4, and 5,

- and the exhausted lamps may be withdrawn at These steps or processes are ac-` shut 0on from the exhaust line by some suitable pincling or clamping means. f v

, When a lamp indexes from station 'I to station 8, it enters the exhaust oven which completely 5 envelops the lamp while it is in positions 8 to I8 inclusive. By causing the lamp to pass through this oven during several of the ushing and exhausting operations, a high purity atmosphere is obtained. An oven similar to that described in the application of Gardner and Allen, filed July 20, 1940, Serial No. 346,618 may be used.

While the lamp is in positions lll, il and i2', it is exhausted through an exhaust line termed on the drawing as exhaust No. 2. After these three exhausting positions, themachine indexes to position- IS where the lamp is connected to exhaust No. 1. However, before the lamp reaches the position I3, yet after it leaves position i2, it establishes contact with another position shown in dotted lines between positions i2 and I3. Although -the machine is indexing at the time, still the connection between the lamp and this auxiliary position is of suicient duration to allow flushing with some inert gas, for example argon, at a relatively low mercury pressure, for example about l m. m. At .position I3, the lamp establishes connection with exhaust No. 1 which pumps out the argon. While at position It, the lamp is evacuated through exhaust No. 2.

Similar flushing and evauating steps vare taken on the several succeeding positions. Between !4 and I5, there is another ushi'ng, similar to the first, with some inert gas, preferably argon, at a relatively low mercury pressure, for example about 10 m. m. At station I5, the lamp f is evacuated through exhaust No. l, and at station I6, through exhaust No. 2. Between I5 and Il there is. an argon iiush. At I l there is. an evacuation through exhaust No. 1 and at I8 there is an evacuation through exhaust No. 2. Between l8 and I9 there is an argon ush. At I9 there is an evacuation through exhaust No. 1 and at there is an evacuation through exhaust No. 2. Between 20 and 2 I there is another argon flush.

At position 2|, the lamp is evacuated through the exhaust No. 3 and at position 22, through the exhaust No. 4. Between 22 and 23, there is an argon iiush. At 23, there is an 'evacuation through exhaust No. 3 and at 24, through exhaust No. 4. Between 24 and 2li, therev is an argon ush. At 25, there is an evacuation through exhaust No. 3 and at 26, there is an evacuation through exhaust No. 4.

Evacuation through exhaust No. i takes place to their respective oxides.

- lamp to discolor.

2 thereafter at positions 21, 28, 29, 20 and 3|. After this continuous evacuation at these vfive positions, the lamp has been sufllciently evacuated to receive its nal filling of gas.

When the lamp reaches position 2l after the several exhausting and flushing Operations and the period spent in the exhaust oven','it,is ready for the filament lighting or cathode breakdown as it is more commonly. called:

'I'he purpose ofthis cathode breakedown is to obtain a cathode with high emission" qualities.` Since one or more of the alkaline'-earth oxides may be used for this purpose, it has been found that barium and strontium oxide is desirable. Since it is advantageous to use a barium and strontium carbonate and lacquer solution, when coating the coiled wire, usually of tungsten, which forms the surface on whichthe barium and strontium oxide is desired. the barium and strontium carbonate and lacquer Amust be broken down so as to leave an active barium strontium oxide with high emissive properties.y

This break-down is accomplished by a series of filament heating steps in which a current hows through the electrodes. The heat generated thereby in the filament will result in the reduction of the barium and strontium carbonates Carbon dioxide and decomposition products of lacquer will be drawn ofi in the gaseous state through exhaust No. 3 and exhaust No. 4.

The lament heating is accomplishedby passing current through a series of incandescent lamps which act as a ballast iimiting the current through the electrodes of the discharge lamp. The Wattage and voltage of these incandescent lamps serving as a ballast will be governed by the purpose for which the filament lighting process was instituted. Since the purpose of this process is to obtain a cathode with -high emissive properties, the cathode must be 'suillciently broken down at the end of the filament. lightingprocess to obtain this result. It is desirable to pass a current through the cathodes that will heat them suiciently .tof result in the reduction of the barium and strontium carbonates to their. respec` tive oxides and yet this current should not be such that the heat generated thereby will cause the tungsten wire to break or the walls of the The voltage must also b e kept below the point where the cathode coating would break up and chip off.

It has been found that for a 40 watt fluorescent lamp, the cathode will be adequately broken down if a schedule similar to the following is used for the incandescent lamps in series:

l 300 volt flash. After the lamp has passed through the rst three lament lighting positions, it is flushed with a small quantity of mercury introduced i therein at position 24. This mercury dispensing means may be similar to that described in the copending application of Gardner and Allen led June 26, 1940, Serial No. 342.472. Although the located at position I'.

lamp is being evacuated at each position the entire filament lighting process, a

amount of mercury remains in the lamp so that. at positions 26 and 21, the lamp may be tested to see whether or not the iilament is properly broken, down. This is done by providingequipment, such as a step-up transformer, connected to these positions, that is suitable to flash the lamps at 300 volts.- One end of the illaments is connected to the line in one of the hashing positions and the other end of the laments is connected to the line in the other flashing position.

This equipment may be similar to the regular starting equipment employed when the lamps are actually in use. This flashing, which also helps to break down the cathode, consists of -a voltage across the cathodes sufllcient to start the discharge across the lamp. If the discharge does not occur, the lamp is faulty. positions 2i and 21 also serves to test the emission qualities of the barium strontium oxide on the lament. Following these two ashing positions, there is one more lighting position, position 28, where an incandescent lamp ballast of wattsvolts-is used.

The upper section of the lamp passes through a preheating oven when it moves through positions 30 to 32, inclusive. This preheating oven is provided to heat the upper part of the lamp and particularly the seal joining the bulb neck to the mount in order-to prevent strains from occurring in the glass of the lamp when it comes in contact with the 'metal of the tipping torch The oven may be of a construction similar to that described in the copending applicationA of Gardner and Allen, filed July 20, 1940, Serial No. 346,618 except that, inasmuch as it only encloses the upper section of the lamp, there is no oven oor or doors.

The lamp is now ready to receive a small amount of mercury that is desirable for the proper operation of an electric gaseous discharge lamp. The mercury may be introduced at position 3l by a mercury dispensing device such as, for example, the one described in the copending application of Gardner and Allen, filed June 26, 1940, Serial No. 342,472.

As the machine indexes from position 3| to position 32, an atmosphere of an inert gas, such as argon, is introduced at a mercury pressure of from 4 to 11 rn. m. When the lamp reaches position 32, it undergoes evacuation through a pressure controlling device similar, for example, to that described in the copending application of Gardner, led May 18, 1940, Serial No. 335,979. Thus the desired pressure usually about 2 m. m. is accurately obtained. The lamp then moves to position I where it is tipped off by a lamp sealing device similar, for example, to that described in the copending application of Gardner and Allen, led June 28, 1940, Serial No. 342,968.

Althoughv this exhaust cycle has been described as having several distinct flushings with an inert gas, the number of flushing operations may bevaried without departing from the essence of the invention.

- Furthermore, different valve construction may This B85111113 at It may -be noted that different exhaust lines are employe'd at different stages during the exhaust cycle. lThis is done to obtain an eiiicient evacuating system and consequently a high purity atmosphere inthe lamp. It will be noted from a study of-the accompanying drawing and the above specifications that exhaust No. 1 is only used directly after an argon flush. Thus the greater part of the argon ush is conned to one line, exhaust No. 1. Exhaust No. 2 is used before there is any flushing at all and thereafter, after most of the argon has been evacuated through exhaust No. 1. Thus exhaust No. 1 is used for the most part to draw oi the argon iiush. Exv haust No. 2 is used to draw off the air present in the lamp after it passes the leak detector, and thereafter to draw off the gases given off by the glass and the fluorescent material while the lamp is passing through the exhaust/oven.

Once the cathode break-down" starts, a different set of exhaust lines are used because these lines will be employed for different purposes than exhaust No. 1 and exhaust No. 2. Exhaust No. 3 is used directly after su'ch argonushes as take place during the lament lighting period. Thus this line will draw off the' argon used in flushing and the carbon dioxide and decomposition products of. lacquer given oi during the cathode break-down. Exhaust No. 4 is used mainly to evacuate the carbon dioxide and decomposition products of the lacquer. Thus, by using four different exhaust lines a maximum' efficiency is obtained in attaining a. high purity atmosphere in the lamp.

Although there are but four different exhaust lines employed in this invention, more lines and pumpsi may be used to'speed up the exhausting process or to adequately exhaust these lamps with a greater cubical content than the specific example given herein.

What we claim is:

1. A process for exhausting discharge lamps having illaxnentary electrodes, said process comprising the following steps: exhausting the lamp to a rough vacuum, baking` the lamp in an oven, exhausting the lamp to a :liner degree of Vacuum, iiushing with an mertfgas, exhausting again on a different pump, lighting the lamentary electrode, placing some mercury in the lamp lling the lamp with an inert gas, exhausting the lamp again, extinguishing Athe lament, further exhausting the lamp, heating the lamp again, placing some mercury in the lamp again, adding an excess pressure of inert gas, evacuating the excess of the inert gas, sealing off the lamp, and removing it from the machine.

2. A process for exhausting discharge lamps having iilamentary electrodes, said process comprising the following steps: exhausting the lamp to a rough vacuum, placing the lamp in an oven, exhausting the lamp to a ner degree of vacuum, flushing with an inert gas at low pressure, then exhausting on a different pump, removing the lamp from the oven, lighting the lamentary electrode, exhausting the lamp on a third pump separate from the other two pumps, placing some mercury in the lamp, iiushing with an inert gas at low pressure, exhausting on a. fourth pump separate from the others, placing the lamp in an oven during the last part of the latter exhausting step, placing some mercury in the lamp, filling with a pressure of inert gaslin excess of that desired in the finished lamp, exhausting said excess, removing the lamp from the oven, sealing oi the lamp and removing it from the machine.

ERNEST c. CURWEN. ROLANDM. GARDNER. 

